BIOB 272 1st Edition Lecture 28Outline of Last Lecture Sexual SelectionI. Adaptation Continueda. Forelimb Geneticsi. Dpp, BMP2, Mm E, MmPrx1, Bat Eii. Shhb. Additional AppendagesII. SEXa. Asexual Reproductionb. Eukaryotic Sexual ReproductionIII. Female Contributions to ReproductionIV. Cost of SexV. Disadvantages of Asexual ReproductionVI. Consequences of Sexual ReproductionVII. Sexual SelectionVIII. Sexual DimorphismIX. Clicker Question- What is a female? What is a Male?X. AnisogamyXI. Why does Sexual Selection OccurThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.XII. Unequal Investment- Unequal Limits on Male and Female FitnessXIII. Rough Skinned Newts Example of Gender Asymmetry= InvestmentXIV. Two Categories of Sexual Selectiona. Male-male competition (intrasexual selection)b. Female Choice (intersexual selection) Outline of Current Lecture Sexual Selection Day 2I. Mating Systems and Sexual Selection- Monogamy- Polygyny- Polyandry- Multi-male – Multi-femaleII. Two Categories of Sexual Selection- Male-male competition- Female ChoiceIII. The mammalian baculumIV. Case Study: The Vestigial Whale PelvisV. Female Choice- Why do females make the choices they do?i. Direct Benefits Hypothesisii. Indirect Benefits HypothesisVI. Case Study 2: MT Bison Range Current LectureSexual Selection Day 2I. Mating Systems and Sexual Selection: high variation in mating success leads to strongsexual selection Increase variation in mating success= increase sexual selection- Monogamy: 1 male, 1 female High parental investment (both) Sexual dimorphism and sexual selection low Often monogamy is social, extra-pair copulations common in many species True monogamy= hard to find. Examples= jackass penguins, prairie voles- Polygyny: 1 male, many females Maternal investment high Sex dimorphism and sexual selection on males high Examples: northern fur seals in Alaska, gorillas- Polyandry: many male, 1 femal Females mate with up to 4 males. Defend their nests against other females. Males care for offspring. Paternal investment=high Sexual selection on females Example: Jacana spinosa- Multi-male – Multi-female: multiple mating in both sexes Common in many species One sex will often show higher variance and thus more intense sexual selection Example: Bonobos and chimpanzeesII. Two Categories of Sexual Selection- Male-male competition(intrasexual selection) Males compete directly for access to mates Traits (weapons) are used against other males1. Combat, Territory and defense of females (pre-copulatory)2. Sperm competition (post copulatory)- often leads to evolution of extremem genital structures to combat competitiono Penis with sperm scoopers- scoop out sperm put in vaginaby other males and then replace with own spermo Sperm competition drives evolution of larger testes3. Infanticide: by killing the offspring of the previous dominant lion, new dominant males can gain reproductive access to all females inthe pride immediatelyo Example: lions4. Alternative Strategies- many of themo “sneaker males”- females spawn eggs and a particular male will spray sperm over those eggs. Sneaker males will do a “drive-by” and spray their own sperm over the females eggs over the other males sperm.- Female Choice (intersexual selection):  Females choose males, males may not interact Trait used mostly for display Female multiple mating selects for male traits that increase paternity- Many cases- both are importantIII. The mammalian baculum- bone in penis of many mammals- many different forms- Use as penis scoop to scoop out sperm from other males in vaginas and replace with own- Female choice drives thisIV. Case Study: The Vestigial Whale Pelvis- Whale pelvis= vestigial structure- loss of most or all of ancestral function (walking) Primary ancestral function of the pelvis (walking) lost completely at least 40MYA Still persists possibly as a vital reproductive function= penis attachment Larger pelvic shape=larger testis sizeV. Female Choice:example: sage grouse lek, bowerbirds= males make “display” groundsfor females, Birds of paradise= visual, predation so low so have much more time for extreme female choice- Why do females make the choices they do? Direct Benefits Hypothesis: females choose males based on actual quality (resources obtained). Example: food for sex in hanging flieso More food= longer sex= more sperm transferred= higher reproductive success Indirect Benefits Hypothesis: “good genes”- females choose males based on genetic quality= offspring qualityo Ornaments are costlyo Large male ornaments may reflect males that are:i. Physiologically robustii. Resistant to parasitesiii. Able to overcome ornament “handicaps”VI. Case Study 2: MT Bison Range- indirect benefits hypothesis- Pronghorn females are VERY choosy.- Females have complete control over mating. Males will fight to death over females.- Strong variation among males in reproductive success- “Attractive” males have higher survival and require fewer